package org.bjf.utils;


import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Arrays;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;


/**
 * MD5加密和验证工具类
 *
 * @author wushen
 * @date 2015-9-23
 * @since 0.0.1
 */
public class MD5Util {

  private static final Logger logger = LoggerFactory.getLogger(MD5Util.class);

  private static final String HEX_NUMS_STR = "0123456789ABCDEF";
  private static final Integer SALT_LENGTH = 12;
  private static final String hexDigits[] = {"0", "1", "2", "3", "4", "5",
      "6", "7", "8", "9", "a", "b", "c", "d", "e", "f"};

  /**
   * 将16进制字符串转换成字节数组
   */
  private static byte[] hexStringToByte(String hex) {
    int len = (hex.length() / 2);
    byte[] result = new byte[len];
    char[] hexChars = hex.toCharArray();
    for (int i = 0; i < len; i++) {
      int pos = i * 2;
      result[i] = (byte) (HEX_NUMS_STR.indexOf(hexChars[pos]) << 4
          | HEX_NUMS_STR.indexOf(hexChars[pos + 1]));
    }
    return result;
  }

  /**
   * 将指定byte数组转换成16进制字符串
   */
  private static String byteToHexString(byte[] b) {
    StringBuffer hexString = new StringBuffer();
    for (int i = 0; i < b.length; i++) {
      String hex = Integer.toHexString(b[i] & 0xFF);
      if (hex.length() == 1) {
        hex = '0' + hex;
      }
      hexString.append(hex.toUpperCase());
    }
    return hexString.toString();
  }

  /**
   * 验证字符串是否与密文相同
   *
   * @param str 需要验证的字符串
   * @param digestStr md5加密后的密文
   * @return boolean
   */
  public static boolean validDigest(String str, String digestStr) {

    boolean result = false;
    try {

      byte[] pwdInDb = hexStringToByte(digestStr);

      byte[] salt = new byte[SALT_LENGTH];

      System.arraycopy(pwdInDb, 0, salt, 0, SALT_LENGTH);

      MessageDigest md = MessageDigest.getInstance("MD5");

      md.update(salt);

      md.update(str.getBytes("UTF-8"));

      byte[] digest = md.digest();

      byte[] digestInDb = new byte[pwdInDb.length - SALT_LENGTH];

      System.arraycopy(pwdInDb, SALT_LENGTH, digestInDb, 0, digestInDb.length);

      result = Arrays.equals(digest, digestInDb);
    } catch (NoSuchAlgorithmException e) {
      logger.error(e.getMessage(), e);
    } catch (UnsupportedEncodingException e) {
      logger.error(e.getMessage(), e);
    }

    return result;
  }

  /**
   * 获得MD5加密后的密文
   *
   * @return MD5加密后的密文
   */
  public static String encode(String str) {
    String encodeStr = null;
    try {

      byte[] pwd = null;

      SecureRandom random = new SecureRandom();

      byte[] salt = new byte[SALT_LENGTH];

      random.nextBytes(salt);

      MessageDigest md = null;

      md = MessageDigest.getInstance("MD5");

      md.update(salt);

      md.update(str.getBytes("UTF-8"));

      byte[] digest = md.digest();

      pwd = new byte[digest.length + SALT_LENGTH];

      System.arraycopy(salt, 0, pwd, 0, SALT_LENGTH);

      System.arraycopy(digest, 0, pwd, SALT_LENGTH, digest.length);

      encodeStr = byteToHexString(pwd);
    } catch (NoSuchAlgorithmException e) {
      logger.error(e.getMessage(), e);
    } catch (UnsupportedEncodingException e) {
      logger.error(e.getMessage(), e);
    }

    return encodeStr;
  }

  public static String encodeWithoutSalt(String str) {
    String encodeStr = null;
    try {

      MessageDigest md = null;

      md = MessageDigest.getInstance("MD5");

      md.update(str.getBytes("UTF-8"));

      byte[] digest = md.digest();

      encodeStr = byteToHexString(digest);
    } catch (NoSuchAlgorithmException e) {
      logger.error(e.getMessage(), e);
    } catch (UnsupportedEncodingException e) {
      logger.error(e.getMessage(), e);
    }

    return encodeStr;
  }

  public static String MD5Encode(String origin, String charsetname) {
    String resultString = null;
    try {
      resultString = new String(origin);
      MessageDigest md = MessageDigest.getInstance("MD5");
      if (charsetname == null || "".equals(charsetname)) {
        resultString = byteArrayToHexString(md.digest(resultString
            .getBytes()));
      } else {
        resultString = byteArrayToHexString(md.digest(resultString
            .getBytes(charsetname)));
      }
    } catch (Exception exception) {
    }
    return resultString;
  }

  private static String byteArrayToHexString(byte b[]) {
    StringBuffer resultSb = new StringBuffer();
    for (int i = 0; i < b.length; i++) {
      resultSb.append(byteToHexString(b[i]));
    }

    return resultSb.toString();
  }

  private static String byteToHexString(byte b) {
    int n = b;
    if (n < 0) {
      n += 256;
    }
    int d1 = n / 16;
    int d2 = n % 16;
    return hexDigits[d1] + hexDigits[d2];
  }

  public static void main(String[] args) throws Exception {
    String str = "12345";
    System.out.println(encode(str));

    System.out.println(encodeWithoutSalt(str));
  }
}  

